1. Field of the Invention
The present invention relates to a coordinate input system and, more particularly, to a coordinate input system which is capable of providing various types of information such as information for varying the size of a coordinate point in accordance with the level of the force applied to an input pen, i.e., the pressure of contact between the input pen and a tablet. The invention also is concerned with an input pen suitable for use in this system.
2. Prior Art and Its Problem
A conventional coordinate input system of the type described has a pressure sensor provided on the input pen or a multiplicity of pressure sensor elements dispersed on the entire area of the input region of a tablet. The pressure sensor is capable of sensing and detecting the "stylus pressure", i.e., the pressure at which the input pen contacts the tablet, and varies the size of the coordinate point in accordance with the pressure detected.
The arrangement having a multiplicity of pressure sensor elements encounters difficulty in obtaining and maintaining uniform pressure sensing characteristics over the entire area of the input region, with the result that the contact pressure of the input cannot be uniformly and correctly detected over the entire area of the input region of the tablet. The arrangement which relies upon the pressure sensor provided on the input pen requires a cable or other suitable means for picking up the pressure sensing information from the input pen, resulting in an inferior maneuverability of the input pen during inputting.